Experimental study on debris-flow velocity control mechanism with baffles in a drainage channel

Debris-flow deceleration baffles can be used to reduce flow velocity in a large gradient drainage channel and the scouring rate of concrete at its bottom to extend its service life. A series of experimental tests were conducted on a single group and a double group of baffles to study the velocity reduction ratio in a 6-m-long flume. Flow density, baffle shape, movement slope, and row spacing were considered in the single-group baffle experiments. Flow pattern and velocity control effects were compared between the single-group and double-group baffles. In this paper, the percentage of velocity attenuation before and after the baffles, namely the velocity reduction ratio (n), is used to quantify the velocity regulation effect of the baffles. The results of the single-group baffle experiment showed that the average velocity reduction ratio tends to increase with the increase of debris-flow density and movement slope. However, the average velocity reduction ratio tends to decrease with the increase of row spacing, and it is the same for the three different shapes of baffles under each slope condition. Comparison between the experimental results of the single and double groups showed that although the double-group baffles cannot continuously reduce the flow velocity of the debris flow, it can control it within a certain range along the flow path, and there will be no debris overflowing the flume. The results help in optimizing the design of the velocity reduction ratio in a debris-flow drainage channel with a large gradient.